Applicant of the present invention have previously proposed in JP-A-10-195494 a method of producing constant weight products made from aerated molten soap as a kind of a compressible fluid which comprises solidifying molten soap containing a large number of bubbles in a cavity of a mold, wherein the step of solidification is carried out in a hermetically closed cavity.
According to this production method, outside air not being allowed to enter the cavity, the solidified soap is prevented from forming voids or depressions. However, because a given volume of molten soap is fed into the cavity, the density of the molten soap is subject to variation with variations of foaming degree of the molten soap or variations of the liquid level of a storage tank containing the molten soap. It follows that the resulting aerated soaps show scatter in weight even though molten soap is fed in, constant volume portions.